Imagine witnessing the untimely death of a vibrant, otherworldly being.

As it succumbs to an invisible menace, this entity’s colors (brilliant shades of amber, magenta, chartreuse) turn fluorescent blue and purple and green before fading to bright white.

As it decays, wisps of sludge drip from the skeletal remains.

Apocalyptic sci-fi?
This is real life, in the documentary “Chasing Coral.”
And it’s an environmental tragedy of our own making, the film heartbreakingly argues, that has little hope of being reversed without immediate human intervention.

Using his 2012 documentary, “Chasing Ice,”in which time-lapse technology showed the melting of glaciers, as his guide, Mr. Orlowski frames “Chasing Coral” with a similar structure.

But setting up time-lapse camera rigs deep underwater off the coasts of Caribbean islands, Hawaii and Australia proved problematic.

At one point, the assembled team of researchers has to document the deadly transformation of the Great Barrier Reef manually: diving with special cameras to meticulously record the day-to-day changes on the ocean floor.